Double-hung window assemblies are well known in the art and generally include a pair of window sashes slidably mounted in a frame. The window sashes are generally movable in parallel planar paths whereby the window opening may be half opened by moving one sash into an overlapping position with the other sash. In normal operation, the lower inner sash, which is the sash moving in the path closest to the interior of the room, is raised and lowered, while the outer sash is generally secured at the upper end of its path. Preferably, the lower sash is capable of being tilted in toward the room area so that the outer surface of its pane may be reached from the interior of the room for washing.
Locking is generally provided by cam locks, such as check rail locks in which the two sashes are mechanically secured to one another when in the closed non-overlapping position to prevent movement relative to one another. These locks are generally required to be disposed on top of the lower sash, which in some installations can be difficult to reach if the window sashes are tall or if the windows are located higher on the wall than normal. Such locks are also susceptible to breaking when subjected to force due to the entire locking occurring at the particular area of the lock. Accordingly, if a potential intruder applies force to the window, the entry force is resisted solely at the point where the sash lock is secured to the sash. Breaking of the lock, or possibly the wooden or PVC sash is a distinct possibility due to the resulting stress concentrations at the lock location.
Further, since locks of the above-described type are generally disposed on top of the inner sash at the middle of the window opening, they can be an undesirable visual intrusion on the view through the window.
Counterbalancing weights or compensating springs are also generally used with the sashes of double-hung window assemblies to aid in raising such sashes. The sashes are typically held in open venting positions by a combination of the counterbalancing weights, or springs, and a frictional-type binding of the sash in its track. Unfortunately, such binding also occurs when moving the sash to thereby increase the effort required to open and close the window. Accordingly, a design balance is required to minimize binding for ease of operation while still maintaining sufficient binding to prevent the sash from falling closed and possibly injuring a person, and more particularly a child, who might have their hands or head in the opening. Of course, even a proper initial design balance will often fail over time, as evidenced by the not uncommon occurrence of older windows which are often times kept open only be wedging something such as a board beneath the sash.
Placing the window sash in an open venting position also requires that the lock be in an unlocked position to permit planar movement of the inner sash relative to the outer sash. As a result, the vented window becomes a security hazard whereby a potential burglar can readily recognize that the window is unlocked and easily raise the sash and gain access to the house.
The present invention is directed toward overcoming one or more of the problems set forth above.